 /*******************************************************************************
  * Copyright (c) 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.core.commands;

 /**
  * <p>
  * A parameter for a command. A parameter identifies a type of information that
  * the command might accept. For example, a "Show View" command might accept the
  * id of a view for display. This parameter also identifies possible values, for
  * display in the user interface.
  * </p>
  *
  * @since 3.1
  */
 public interface IParameter {

     /**
      * Returns the identifier for this parameter.
      *
      * @return The identifier; never <code>null</code>.
      */
     public String getId();

     /**
      * Returns the human-readable name for this parameter.
      *
      * @return The parameter name; never <code>null</code>.
      */
     public String getName();

     /**
      * Returns the values associated with this parameter.
      *
      * @return The values associated with this parameter. This must not be
      * <code>null</code>.
      * @throws ParameterValuesException
      * If the values can't be retrieved for some reason.
      */
     public IParameterValues getValues() throws ParameterValuesException;

     /**
      * Returns whether parameter is optional. Otherwise, it is required.
      *
      * @return <code>true</code> if the parameter is optional;
      * <code>false</code> if it is required.
      */
     public boolean isOptional();
 }

